1. Field of the Invention
The invention relates to X-ray machine calibration devices, and specifically in an improved X-ray phantom.
2. Description of the Prior Art
X-ray phantoms are known calibration devices and teaching aids for conventional X-ray machines. The prior art phantoms are available in a number of variations, some being plastic replicas of the human body or specific portions thereof, while others consist of actual human bones cast in plastic. These phantoms are used to train X-ray technicians in the proper positioning of the human body for the various X-ray pictures that are taken for diagnosis, and the resulting films may be studied to aid in calibrating the X-ray machine and identifying the radiographic image of known structures.
The structure of prior art phantoms has uniformly been solid, as taught in U.S. Pat. No. 3,348,319 to Harrison, A problem with any solid phantom is that the user is limited by those objects that the manufacturer has placed within it. In addition, the solid phantom is unlike the human body, which is mostly liquid and contains air spaces. In an effort to simulate the radioequivalent of the human body, manufacturers have tried many plastic materials and often have molded air spaces into a human replica.
One of the primary problems in the use of an X-ray machine is proper calibration. The radiation does must be adjusted for both proper penetrating power and intensity for each different application. The established setting for a given job may very with a different film, different film holder, or other equipment change. At times, a machine must be adjusted to locate a special object in a patient's body, such as broken needle or catheter. Traditional phantoms lack versatility for critical adjustment in these special situations.
Some of the other difficulties encountered with fullbody phantoms include extremely difficult handling because of the weight of the synthetic construction materials; positioning of examinations of joints is limited because of metallic parts needed to hold the joints together, and these metallic parts interfere with the accuracy of the finished radiograph; the mock body organs placed is a solid phantom are not realistic and it is difficult to remove contrast media placed in these organs; the skeletons used in full body phantoms are osteoporotic and finished radiographs of the extremities lack proper radiographic contrast and density; and chest and abdomen also lack accuracy in radiographic contrast and density.
Some of the difficulties encountered with disarticulated phantoms such as bones cast in plastic include unrealistic radiographic density and contrast because of a lack of fatty tissue and gas patterns as are seen in human radiographs of the pelvis. There are generally only two densities in the radiographs of such phantoms: one for bone and one for overall soft tissue, the latter of which may be absent entirely. Skull phantoms lack significant air in the sinuses and mastoid cells to provide additional densities.
Many of the noted problems are directly related to the lack of a superior means of accurately simulating various densities found in the human body, while other problems relate to the difficulty in locating and removing contrast media and other desired subject matter in an environment simulating the human body. These problems and others are solved with the present x-ray phantom.